Re: [PATCH 3/4] sched/numa: Apply imbalance limitations consistently

Mel Gorman
2022-05-18T15:40:03Z

On Wed, May 18, 2022 at 03:59:34PM +0200, Peter Zijlstra wrote:
> On Wed, May 18, 2022 at 11:46:52AM +0100, Mel Gorman wrote:
>
> > > (Although I do wonder about that 25% figure in the comment; that doesn't
> > > seem to relate to any actual code anymore)
> > >
> >
> > You're right, by the end of the series it's completely inaccurate and
> > currently it's not accurate if there are multiple LLCs per node. I
> > adjusted the wording to "Allow a NUMA imbalance if busy CPUs is less
> > than the maximum threshold. Above this threshold, individual tasks may
> > be contending for both memory bandwidth and any shared HT resources."
> >
>
> Looks good. Meanwhile I saw a 0-day complaint that this regresses
> something something unixbench by a bit. Do we care enough? I suppose
> this is one of those trade-off patches again, win some, loose some.

I think it's a trade-off. I made a more complete response to the 0-day
people at https://lore.kernel.org/all/20220518152258.GR3441@techsingularity.net/

--
Mel Gorman
SUSE Labs